干旱区绿洲荒漠带土壤水盐异质性及生态环境效应研究——以黑河中游张掖绿洲为例

 对黑河中游地区典型绿洲的土壤含水量与含盐量分析表明,在无灌溉情况下,绿洲及绿洲边缘过渡带表层土壤含水量水平分异明显,由绿洲区的20%左右递减到绿洲荒漠生态过渡带的2.9%。绿洲荒漠带土壤水分变化反映了人类利用绿洲水资源的程度,在绿洲地下水资源开发过度和绿洲边缘人类活动剧烈的区域均存在着生态裂谷,对绿洲生态系统的稳定极为不利。绿洲荒漠带土壤可溶性盐分含量的水平分异表现为绿洲土壤可溶性盐分含量比绿洲荒漠生态过渡带和荒漠区低;绿洲界外区不同荒漠类型土壤含盐量变化不同,在绿洲外围沙质荒漠区,土壤含盐量较低,在绿洲外围砾质荒漠（戈壁）区,土壤含盐量明显高于绿洲区;荒漠区土壤含盐量的垂直变化表明,含盐量最高的聚集层一般不在表层,而在40～60 cm的亚表层。受土壤水盐分异的影响,绿洲外围荒漠植被类型出现分异,从高位绿洲到中位绿洲,外围区荒漠植被的耐旱性和耐盐性均增加。

Heterogeneity of Soil Moisture and Salt Contents and Its Eco-environmental Effects in Oasis-desert Belt in Arid Zone--Taking Zhangye Oasis in the Middle Reaches of Heihe River as A Case Study

The soil moisture and salt contents analysis for representative oases in the middle reaches of Heihe River presented in this paper shows that the horizontal diversity of topsoil moisture content in oasis-desert belt is distinct under no irrigation condition, that is, the topsoil moisture content reduces from 20% of oasis to 2.9% of oasis-desert ecotone. The change of soil moisture content in oasis-desert belt reflects the utilization degree of water resources. Where is over extracting of groundwater and human intensive activities where exists \!ecological gap\", which is disadvantageous to the stabilization of oasis ecosystem. The horizontal variance of soil dissoluble salt contents indicates that salt contents in oasis soil are lower than that in ecotone soil and desert soil. Besides, the soil salt contents are different in desert types outside oasis, that is, the soil salt content in sandy desert is lower than that in the Gobi. The vertical profiles of desert soil salt content indicate that the higher salt content is not in the surface layer but in the subsurface layer of 40～60 cm. The soil moisture and salt content variances have resulted in the deserta diversity outside oasis, the drought-tolerance and salt-tolerance of deserta increase gradually from oasis in higher place to oasis in mid-position.